Linear papules appear on a boy’s thumb, wrist

Figure

The case

A healthy 6-year-old boy presents for evaluation with a 3-month history of an asymptomatic rash extending from his left thumb to his left wrist (Figure).

Diagnosis: Lichen Striatus

Discussion

Lichen striatus is an uncommon condition that usually affects children aged to 15 years. It often presents as a linear band of inflammatory flat-topped papules ranging in color from pink to skin-colored to tan and often resolves with postinflammatory hypopigmentation. The linear arrangement of the papules characteristically follows Blaschko’s lines and can present in a continuous band or with interrupted areas. The distribution along Blaschko’s lines points to a somatic mosaicism pathogenesis, but neither the involved genes nor the inciting factors are known.¹ The papules tend to be asymptomatic but occasionally have associated pruritis.

Lichen striatus usually appears on the extremities and less commonly on the trunk, face, neck, or buttocks. Lichen striatus rarely affects the nail, but when it does it is almost exclusively seen in children. Unlike lichen planus that can affect the whole nail, lichen striatus involves just the medial or lateral portion and may result in onycholysis, splitting, longitudinal ridging, fraying, or, rarely, total nail loss.²

The condition tends to appear abruptly and reaches its maximum extent within a few days to weeks (occasionally up to several months), then spontaneously resolves over a period of a few months to 2 to 3 years. The resulting postinflammatory hypopigmentation can take a year or more to disappear. In individuals with darker skin tones, lichen striatus may not be noticeable until the appearance of a resolving band of hypopigmentation.¹ Recurrences of lichen striatus are unusual.³

Histopathology

The histological findings of lichen striatus can vary depending on which part of the linear band is biopsied, and how long the lesion has been present.¹ However, most cases display a combination of spongiotic and lichenoid interface dermatitis with perivascular and periadnexal lymphocytic infiltrate present in the dermis.³ The infiltrate can surround eccrine sweat glands, ducts, and hair follicles distinguishing it from lichen planus.²

Epidermal changes include hyperkeratosis, focal parakeratosis, intercellular and intracellular edema, focal spongiosis, and lymphocytic exocytosis.^1,3 Dyskeratotic keratinocytes also can be found in the granular and horny layers or at the level of the dermoepidermal junction.

Differential diagnosis

The differential diagnosis includes linear lichen planus (LP), blaschkitis, linear graft versus host disease (GVHD), linear epidermal nevus, lichen nitidus, and other inflammatory disorders in a linear pattern such as linear porokeratosis, and linear psoriasis. Blaschkitis more often favors the trunk, has multiple streaks, and presents in adults,⁴ and linear GVHD occurs in a specific clinical setting. Although lichen striatus and linear LP can look similar histologically, their clinical appearance is what sets them apart. Hypopigmentation is the most common sequala of lichen striatus, whereas linear lichen planus resolves with hyperpigmentation.¹ If lichen striatus persists beyond a year’s time, a biopsy can help distinguish lichen striatus from other entities.

Management

Lichen striatus is a benign, transitory condition not requiring treatment unless the lesion is pruritic, in which case topical steroids or nonsteroidal antiinflammatory agents such as calcineurin inhibitors can be prescribed.^3-5

Patient outcome

For this patient, lichen striatus was diagnosed clinically and no further workup was required. The natural history of the disease was discussed with the family, and they elected to have the boy followed clinically without treatment.

References:

1. Shiohara T, Kano Y. Lichen planus and lichenoid dermatoses. In: Bolognia J, Jorizzo J, Schaffer J, eds. Dermatology. 3rd ed. Philadelphia: Elsevier/Saunders; 2012:183-202.

2. Tilly JJ, Drolet BA, Esterly NB. Lichenoid eruptions in children. J Am Acad Dermatol.2004;51(4):606-624.

3. Graham JN, Hossler EW. Lichen striatus. Cutis. 2016;97(2):86;120;122.

4. Mu EW, Abuav R, Cohen BA. Facial lichen striatus in children: retracing the lines of Blaschko. Pediatr Dermatol. 2013;30(3):364-366.

5. Goyal S, Cohen BA. Pathological case of the month. Lichen striatus. Arch Pediatr Adolesc Med. 2001;155(2):197-198.